The use of organic hydroperoxides in the epoxidation of olefins is known to offer important and distinct advantages over other methods of olefin oxide production. Organic hydroperoxides are relatively inexpensive and convenient and safe to handle. In addition, organic hydroperoxides can readily be obtained and maintained in anhydrous form, thus minimizing potential olefin oxide recovery and purification problems. Also, during the epoxidation reaction, the organic hydroperoxide is converted to other valuable products.
A variety of catalysts has been employed for the reaction of olefins with hydroperoxides. One process is that of Smith, U.S. Pat. No. 2,754,325, issued July 10, 1956, wherein soluble heteropoly acids containing transition metals such as chromium, molybdenum and tungsten are employed as homogeneous catalysts for the reaction of olefins and peroxides such as organic hydroperoxides and hydrogen peroxide. More recently, U.S. Pat. No. 3,350,422 and U.S. Pat. No. 3,351,635, issued Oct. 31, 1967, and Nov. 7, 1967, respectively, to Kollar describe the use of solutions of transition metal compounds (V, Mo, W, Ti, Nb, Ta, Re, Se, Zr, Te and U) as homogeneous catalysts. Although sufficiently soluble compounds of those transition metals generally may be suitable as homogeneous catalysts, their commonly available insoluble compounds, especially inorganic, in general are ineffective as catalysts. For Example, U.S. Pat. No. 3,350,422 discloses that epoxidation of propylene with cumene hydroperoxide employing insoluble vanadium pentoxide as catalyst results in a propylene oxide yield (6%) which is little better than that obtained with no catalyst (4%). Similarly, inorganic compounds, particularly the oxides, of the metals disclosed in U.S. Pat. No. 3,351,635, are generally ineffective as heterogeneous catalysts. For example, as the result of experimentation, it has been found that in the reaction of 1-octene with t-butylhydroperoxide, a commercial TiO.sub.2 gave a 50% conversion of hydroperoxide but essentially zero selectivity to 1-octene oxide; ZrO.sub.2 gave a 76.7% conversion of hydroperoxide and essentially zero selectivity to 1-octene oxide; Ta.sub.2 O.sub.5 gave a 11% conversion of hydroperoxide but only a 5% selectivity to 1-octene oxide; CrO.sub.3 gave a 99% conversion of hydroperoxide but only a 22% selectivity to 1-octene oxide; WO.sub.3 gave an 85% conversion of hydroperoxide but only an 8% selectivity to 1-octene oxide; Re.sub.2 O.sub.7 gave an essentially quantitative conversion of hydroperoxide but essentially zero selectivity to 1-octene oxide; TeO.sub.2 gave a 33% conversion of hydroperoxide but only a 7% selectivity to 1-octene oxide; SeO.sub.2 gave a 97% conversion of hydroperoxide but essentially a zero selectivity to 1-octene oxide and UO.sub.2 gave a 55% conversion of hydroperoxide but only 5% selectivity to 1-octene oxide. It would be of advantage, however, to effect the epoxidation of olefins with insoluble catalysts in a heterogeneous system, i.e., catalyst compositions which are substantially insoluble in the reaction mixture since heterogeneous catalyst systems generally exhibit a number of operational advantages for large-scale industrial operations. For example, heterogeneous catalyst systems do not require elaborate means for separation of catalyst composition and reaction products due to the insolubility of the catalyst composition in the reaction mixture.